This proposal is for preclinical development of a DNA tolerizing vaccine to treat multiple sclerosis (MS), a T cell-mediated autoimmune disease for which current therapies are marginally effective. DNA vaccines are a powerful tool to elicit immune responses, and were initially developed as protective vaccines against infection. More recently, DNA vaccines have proven an extremely effective method for treatment of autoimmune disease. DNA tolerizing vaccines encoding autoantigens specifically turn off pathogenic autoimmune responses, leaving the global immune system intact. The mechanism by which antigen-specific DNA therapy modulates disease is through deviation of autoreactive T lymphocytes from a disease-promoting Th1 phenotype to a disease-ameliorating Th2 phenotype. To further develop this technology, SunVax will optimize the DNA vaccine plasmid vector and determine the minimal dosing regimen for inducing immune tolerance, using the experimental autoimmune encephalomyelitis (EAE) animal model for MS. Once the optimal vector backbone is identified, SunVax will generate DNA tolerizing vaccine constructs encoding human myelin antigens. Upon meeting these primary milestones, Phase II of this SBIR will focus on developing molecules that enhance the effects of DNA tolerizing vaccines and completing the preclinical toxicity studies in animals necessary to file an investigational new drug (IND) application with the U.S. FDA. PROPOSED COMMERCIAL APPLICATION: The proposed studies are for the development of a DNA tolerizing vaccine for MS, which affects 350,000 people in the U.S. There is a $1B U.S. market for an effective therapy for MS, with currently available therapies having only marginal efficacy. Through these studies, Sun Vax will complete the animal model preclinical development studies needed to file an investigational new drug (IND) application with the U.S. FDA for the evaluation of a DNA tolerizing vaccine in a phase I clinical trial.